clear;clc
syms s L R 
syms Kp Ki
syms wn zeta

assume(L>0)
assume(R>0)
assume(Kp>0)
assume(Ki>0)
assume(wn>0)
assume(zeta>0)

%%solve
syms B C
equ = [B*C==L/Ki,...
       B+C==(Kp+R)/Ki]
[B,C] = solve(equ,[B,C])